Tube bending tool

ABSTRACT

A tool for bending hollow tubes includes a rotatably mounted bearing element having an abutment element for rigidly grasping the tube. A steering element having a circular periphery is attached to the bearing element. The periphery of the steering element has a non-circular groove. A bending guide having a noncircular groove is positioned over the tube to face the steering element. The two grooves form therebetween a non-circular channel. A handle and a linkage system are connected to the steering element and bending guide to selectively cause the bending guide to be rotated around the periphery of the steering element and to maintain the tube within the channel during the bending.

mited States Patent 1 A Fjelistrom 1 1 TUBE BENDING T001,

{76] Inventor: Bengt Fjellstrom, Vadsbrovagen 12,

Jarna, Sweden [22] Filed: Nov. 2, 1971 [21] Appl. No.: 165,824

[ 30] Foreign Application Priority Data Primary Brownian-Milton S. 0hr Attorney-E. F. Wenderoth et alv [57] ABSTRACT A tool for bending hollow tubes includes a rotatably mounted bearing element having an abutment element for rigidly grasping the tube. A steering element having a circular periphery is attached to the bearing element. The periphery of the steering element has a non-circular groove. A bending guide having a noncircular groove is positioned over the tube to face the steering element. The two grooves form therebetween a non-circular channel. A handle and a linkage system are connected to the steering element and bending guide to selectively cause the bending guide to be rotated around the periphery of the steering element and to maintain the tube within the channel during the bending.

8 Claims, 2 Drawing Figures TUBE BENDING TOOL BACKGROUND OF THE INVENTION The present invention relates to a tube bending tool and more particularly to a tool for bending of tubes having a circular or a substantially circular crosssection. Furthermore, the present invention relates to a tube bending tool for bending tubes in complicated configurations involving predetermined lengths of tubes and bending angles.

Disadvantages involving known tube bending tools are well known. When bending a tube according to known techniques the tube tends to be flattened out. Therefore, the tension varies in different positions of the cross section of a tube during bending, and the wall thickness of the tube will vary radically. Furthermore, the flattening of the tube can lead to cracking along the sides of the tube. v

The object of the present invention is to provide a tube bending tool, in which the above-mentioned disadvantages are eliminated and wherein the use of a mandrel or other means in the inside of the tube during the bending of the tube is not required.

The invention will be described in detail with reference to the appended drawings, where one form according to the invention is shown only as an example.

BRIEF DESCRIPTION OE THE DRAWINGS FIG. 1 is a side elevational-vie of a tube bending tool according to the present invention; and

FIG. 2 is a cross-sectional view taken along line 1-] of FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION A hearing box or bearing member 13 is pivotably mounted to a frame element (not shown). The bearing box or bearing member 13 is selectively pivotably arranged around the axis of the entire tool, which coincides with the axis of the tube intended to be bent. A semi-circular steering element 3 is fitted to the bearing element 13 by means of a screw 12. Steering element 3 is provided with a groove 18. An abutment member 1' is provided to abut the 'tube' 15 by means of a locking screw 11.

Above the .part of the tube which is intended to be bent, is positioned a bending guide 2 arranged for abutting the tube or to be brought into contact with the tube. Bending guide 2 also is provided with a groove 17. A linkage system consisting of levers 4, 7, 6 and 8 and a handle lever 5 is provided for imparting the necessary force required for bending the tube. The lever 6 is attached via joints 4 and 6 to levers 4 and 7, respec tively,'while the lever 8 in a corresponding way is attached via. joints 8 and 8" to the levers 4 and 7, respectively. Rolls and 9 are pivotally attached via joints 10' and 9' to the levers 7 and 4, respectively. The rolls Y10 and 9 are provided for transferring the necessary through the centerlines of the joints 10' and the pins 14 will always provide a cross-section as shown in FIG. 2. Accordingly, during bending the roll [0 always will exert a pressure perpendicular to the bending guide 2 and the tube 15 in a direction towards the centerline of the pins 14 in the steering element.

The grooves 17 and 18 are so arranged that they together counteract any tendency of the tube to flatten when bending thetube without using a mandrel. The channel formed by grooves 17 and 18 between the bending guide 2 and the steering element 3 accordingly exert a pressure on that part of the tube which otherwise could be flattened to counteract such flattening. Therefore, the co-operating grooves 17 and 18 do not form a circular channel, but rather a non-circular channel preferably in the form of an ellipse or a hyperbola.

The breadth a of the co-operating grooves 17 and 18 and the resultant channel between the bending guide 2 and the steering element 3 must accordingly always be less than the depth b (FIG. 2). Considering the crosssection of the channel formed by grooves 17 and 18 the radius of curvature of the channel varies continuously in every sector constituting a quarter (half of a groove) thereof. The grooves in the bending guide 2 and the steering element 3 need not have identical configurations. Accordingly, the groove 17 may have the form of a deeper half ellipse or hyperbola, while the groove 18 could have the same form but less depth.

When conducting a bending operation, the tube 15 will be fixed to the bearing box or bearing member 13 by me ns of the abutment member 1 and the locking screw 11. The bearing member will be rotated to align the bend in the desired plane of the tube, and then it is fixed by means of, for example, locking screws. The linkage system with the bending guide 2 is then attached to the tube bending tool, after which the hand lever 5 is moved downwardly until the desired bending angle is obtained.

Tubes bent by means of the tube bending tool according to the invention do not exhibit flattened portions. Likewise, they have an even wall thickness-Furthermore, the tension in the tube is constant from one portion of the bend to another, because there do not exist friction forces in these portions, which forces appear in bending of tubes with a conventional bending tool.

It will be evident for those skilled in the art that the tool according to the invention and the configuration of the grooves or the channel formed between the bending guide and the steering element can be modified in several ways without departing from the spirit or the scope of the invention.

the steering element 3 and the groove or channel which is formed therebetween by the grooves 17 and 18 when the bending guide 2 and the steering element 3 are positioned in parallel. When bending a tube, a plane I claim:

1. A tool for bending hollow tubes having a substantially circular cross-section, said tool comprising:

a bearing element rotatably mounted and adapted to support a tube to be bent, said bearing element having an abutment element for rigidly grasping said tube;

a steering element attachable to said bearing element, at least a portion of the periphery of said steering element having the form of a circular are, said periphery having therein a groove, the crosssectional arc of which is non-circular, positioned to contact said tube during the bending thereof;

a longitudinal bending guide having a bottom groove, the cross-sectional arc of which is non-circular,

therein, said bending guide positionable in overlying relationship on said tube to face said steering element;

the grooves of said steering element and said bending guide forming a channel, the cross-section of which is non-circular; and

a force applying means engageable with said steering element and said bending guide for selectively forcing said bending guide to rotate around the periphery of said steering element, thereby bending said tube while maintaining said tube within said channel.

2. A tool as claimed in claim I, wherein said force applying means comprises:

a handle; and

a linkage system connected to said handle and including a first lever attachable to the radial center of said steering element, first roller means on said first lever and engageable with said bending guide, a second lever interconnected to said first lever, and second roller means on said second lever and engageable with said bending guide.

3. A tool as claimed in claim 2, wherein said second roller means at all positions thereof exerts pressure on said bending guide in a line perpendicular thereto, said line lying in a plane perpendicular to a tangent of said periphery of said steering element, said plane passing through said radial center of said steering element, and said bending guide being parallel to said tangent during bending of said tube.

4. A tool as claimed in claim 1, wherein the breadth of the cross-section of said channel is greater than the depth thereof, and wherein the radius of the arc of said cross-section of said channel varies from each adjacent quarter sector thereof.

5. A tool as claimed in claim 1, wherein said crosssectional arc of said groove in said steering element is an ellipse 6. A tool as claimed in claim 1, wherein said crosssectional arc of said groove in said steering element is a hyperbola.

7. A tool as claimed in claim I, wherein said crosssectional arc of said groove is said bending guide is an ellipse.

8. A tool as claimed in claim 1, wherein said cross sectional arc of said groove in said bending guide is a hyperbola. 

1. A tool for bending hollow tubes having a substantially circular cross-section, said tool comprising: a bearing element rotatably mounted and adapted to support a tube to be bent, said bearing element having an abutment element for rigidly grasping said tube; a steering element attachable to said bearing element, at least a portion of the periphery of said steering element having the form of a circular arc, said periphery having therein a groove, the cross-sectional arc of which is non-circular, positioned to contact said tube during the bending thereof; a longitudinal bending guide having a bottom groove, the crosssectional arc of which is non-circular, therein, said bending guide positionable in overlying relationship on said tube to face said steering element; the grooves of said steering element and said bending guide forming a channel, the cross-section of which is non-circular; and a force applying means engageable with said steering element and said bending guide for Selectively forcing said bending guide to rotate around the periphery of said steering element, thereby bending said tube while maintaining said tube within said channel.
 2. A tool as claimed in claim 1, wherein said force applying means comprises: a handle; and a linkage system connected to said handle and including a first lever attachable to the radial center of said steering element, first roller means on said first lever and engageable with said bending guide, a second lever interconnected to said first lever, and second roller means on said second lever and engageable with said bending guide.
 3. A tool as claimed in claim 2, wherein said second roller means at all positions thereof exerts pressure on said bending guide in a line perpendicular thereto, said line lying in a plane perpendicular to a tangent of said periphery of said steering element, said plane passing through said radial center of said steering element, and said bending guide being parallel to said tangent during bending of said tube.
 4. A tool as claimed in claim 1, wherein the breadth of the cross-section of said channel is greater than the depth thereof, and wherein the radius of the arc of said cross-section of said channel varies from each adjacent quarter sector thereof.
 5. A tool as claimed in claim 1, wherein said cross-sectional arc of said groove in said steering element is an ellipse.
 6. A tool as claimed in claim 1, wherein said cross-sectional arc of said groove in said steering element is a hyperbola.
 7. A tool as claimed in claim 1, wherein said cross-sectional arc of said groove is said bending guide is an ellipse.
 8. A tool as claimed in claim 1, wherein said cross sectional arc of said groove in said bending guide is a hyperbola. 